Conventionally, an inkjet printer serving as a droplet ejecting device is provided with an inkjet head having nozzles for each of colors in black, cyan, magenta, and yellow, and the nozzles eject ink droplets in each color toward printing paper for printing an image and the like onto the printing paper.
In such an inkjet printer, there has been a problem that ink cannot be ejected from the nozzles due to the causes of an increase in viscosity of ink within an ink channel of the inkjet head, entering of an air bubble into the ink channel.
Hence, a common inkjet printer is configured to perform a purge operation of forcibly discharging ink within the ink channel, thereby discharging ink with increased viscosity and an air bubble within the ink channel, so that ink droplets can be ejected normally through the nozzles.
There are several methods of sucking ink with an inkjet printer that performs such a purge operation. One of the methods is to discharge ink through all the nozzles simultaneously in order to shorten the time of the purge operation.
However, in this purge operation, ink is also discharged through normal nozzles, which increases the amount of ink discharged wastefully.
Accordingly, one proposed printer is configured in such a manner that ink is discharged only through the nozzles that require a purge operation, in order to reduce the consumption of wasted ink during the purge operation.
Japanese Patent Application Publication No. 2005-262821 (see FIG. 7) disclose an inkjet printer including a print head, a cap member, and a carriage. The print head is provided with nozzle arrays capable of ejecting ink in four colors, one nozzle array being provided for each of the four colors. The cap member includes a first cap section capable of sealing the nozzle arrays for three colors and a second cap section capable of sealing the nozzle array for one color. Each of the first cap section and the second cap section has a predetermined open surface. The carriage moves the print head relative to the cap member. The carriage is provided with an optical sensor that is capable of detecting a dot pattern of a recording medium.
Here, when executing a missing-dot check for detecting whether ink droplets are normally ejected through the nozzles, after printing a dot pattern for the missing-dot check on a recording medium, a control unit of the inkjet printer controls the optical sensor to detect the dot pattern on the recording medium.
After the detection, if nozzles with missing dots are detected in each of the nozzle arrays for all the colors, the first cap section and the second cap section can seal the nozzle arrays for all the colors for performing a purge operation simultaneously.
In contrast, if nozzles with missing dots are detected only in the nozzle array for one color, the print head is positioned so that the second cap section is in confrontation with the above-described nozzle array, and the second cap section seals only the nozzle array including the nozzles with missing dots for performing a purge operation.
Accordingly, the inkjet printer can perform a purge operation simultaneously for all the colors, and also can perform a purge operation by selecting the nozzle array for one color. Thus, the time of the purge operation can be shortened, and the consumption amount of wasted ink can be reduced.